Machines such as dozers, loaders, excavators and other types of machinery typically include a hydro-mechanical power transmission system to transfer power, e.g., torque and rotational speed generated by a power source, to one or more connected loads, e.g., a machine tool or attachment. A major component of these hydro-mechanical power transmission systems is a hydraulic pump.
One type of hydraulic pump is a side by side hydraulic piston pump, which comprises a pump housing defining a gear cavity housing, a spur gear set, and a pump cavity housing a pair of pumps. The gear cavity houses side by side spur gears. The pump cavity houses a drive pump and an idler pump. Both pumps are piston pumps, in which reciprocating pistons are arranged within a pump barrel which is operably connected to a rotating shaft. The drive pump may be connected to a crankshaft and thus is driven by a motor or other power source. The idler pump is connected to an idler shaft which is connected to the crankshaft via the spur gear set. The pistons within each pump extend outwardly from one end of each pump barrel and impinge on a cam plate. As the barrel and pistons rotate, the pistons reciprocate, causing hydraulic fluid located on the side of the piston within the pump housing to exit the pump under pressure.
The spur gear set transmits power from the crankshaft to the idler shaft and thus to the idler pump. A drive gear located in the gear cavity and affixed to the end of the drive shaft opposite the drive pump barrel meshes with, and transmits power to, an idler gear, causing the idler gear to rotate, which in turn rotates the idler pump.
The pump cavities are filled with lubricating fluid which surrounds the pumps, shafts and spur gears. The pump housing surrounds the spur gears and also provides channels for the fluid to move around each gear as the gears turn. One gear turns clockwise while the other gear turns counterclockwise. As the gears turn they move the surrounding fluid within the gear cavity in their direction of movement. Oil churned by these spur gears can cause a power loss. Where the gears mesh, the churning fluid causes some resistance because of the limited space for movement of the fluid. This churning represents a parasitic load on the machine power source and can result in a power loss. This power loss can be on the order of 0.4 kW.
The present disclosure is directed toward one or more of the problems set forth above.